For more than half a century amphotericin B (AmB) has served as the gold standard for treating systemic fungal infections. AmB has a broad spectrum of activity, is fungicidal, and is effective even against fungal strains that are resistant to multiple other agents. Surprisingly, clinically significant microbial resistance has remained exceptionally rare while resistance to next generation antifungals has appeared within just a few years of their clinical introduction. Unfortunately, AmB is also highly toxic. Deray, G, J Antimicrob Chemother 49 Suppl 1: 37-41 (2002). Thus, the effective treatment of systemic fungal infections with AmB is all too often precluded, not by a lack of efficacy, but by dose-limiting side effects. Mora-Duarte, J et al., N Engl J Med 347: 2020-9 (2002). Some progress has been made using liposome delivery systems, but these treatments are prohibitively expensive and significant toxicities remain. Wong-Beringer, A et al., Clin Infect Dis 27: 603-18 (1998). Thus, a need exists for an effective but less toxic form or derivative of AmB.